Materials

Instructions

1. Make four cylinders by wrapping ordinary printer paper around the core from a role of paper towel and secure the ends with sticky tape, both inside and out. Next, make four square columns with approximately the same diameter by simply folding the paper, then securing with sticky tape.

2. On a table, arrange the four cylindrical columns so they are standing in a rectangle. Arrange the four square columns in a similar rectangle beside the cylinders.

3. Start stacking books on top of both types of columns one at a time.

4. The square columns will collapse first. Keep the books you loaded onto the square columns aside for later comparison with the weight supported by the cylinders.

5. Keep stacking books on top of the cylinders. They will hold four to five times more weight before collapsing.

Teacher notes

In this demonstration, students learn that significantly more strength can be obtained from the same type and the same quantity of building materials simply by choosing the correct shape.

The walls of a cylinder are free of edges where the force of a compressing load can become concentrated so the load is carried nearly equally by all parts of the cylinder. In other words, all parts of the cylinder share the load.

Secondly, cylinders do not deform easily under an increasing load so that all parts continue to contribute strength until finally collapsing.

In square columns, the load soon deforms the walls so that the weight is soon being carried only at the edges with the remaining parts of the wall not contributing to the total strength.